Generally, a sub frame located under a vehicle body is mounted to the vehicle body via damping or vibration-absorbing elastic assemblies. Subframe mounting structures which are constructed to fix a front end portion, middle portion and rear end portion of a subframe, located under a vehicle body, to the vehicle body via respective elastic assemblies are known as disclosed, for example, in Japanese Patent Application Laid-Open Publication No. 2004-98799 (JP 2004-98799 A).
Particularly, the elastic assembly of the middle portion (hereinafter referred to as “middle elastic assembly”) of the subframe disclosed in JP 2004-98799 A comprises a pair of upper and lower metal plates extending horizontally, and a damping or vibration-absorbing elastic member formed, for example, of rubber and integrally molded with and between the upper and lower horizontal metal plates. The upper metal plate is fixedly mounted, by means of a bolt, to the lower surface of the vehicle body via a cylindrical collar extending upward from the upper surface of the upper metal plate. The lower metal plate is fixedly mounted, by means of a plurality of bolts, to a side surface of the subframe. However, with the technique disclosed in JP 2004-98799 A, there are certain limitations in enhancing durability of the elastic member against a load acting from the subframe.
In many cases, the middle elastic assembly is mounted to the vehicle body before it is mounted to the subframe, for convenience of assembly work. The middle elastic assembly is fixed to the vehicle body by the single bolt, passed through the cylindrical collar, being screwed into the vehicle body. However, during the screwing of the bolt, the collar may undesirably rotate in the same direction as the bolt; namely, there may occur undesired corotation of the middle elastic assembly. Due to such corotation, the middle elastic assembly cannot be mounted to the subframe in a predetermined orientation relative to the subframe.
In general, some rotation-preventing member is fixed to the upper end of the collar by welding or otherwise. By engaging the rotation-preventing member with the vehicle body, it is possible to prevent the collar from corotating with the bolt.
In manufacturing the middle elastic assembly, the elastic member is formed by setting the upper and lower metal plates and collar into a mold, pouring a rubber composition into cavities formed inside the mold and then causing the rubber composition to cure. However, if a rotation-preventing member is fixed to the upper end of the collar as noted above, the mold has to be complicated in construction. Namely, the mold has to be constructed so as not to interfere with the rotation-preventing member when being opened or closed. As one conceivable way to avoid the mold from interfering with the rotation-preventing member, sliding dies openable and closable in a horizontal or left-right direction may be provided in addition to the mold openable and closable in a vertical or up-down direction, in which case, however, the mold would become complicated in construction. Further, merely providing the sliding dies may undesirably produce, on the outer surface of the elastic member, burrs resulting from mating surfaces of the sliding dies (i.e., parting line between the sliding dies), and such burrs are not preferable in enhancing durability of the elastic member.